1. Field of the Invention
The present invention relates to a method and device utilized in a wireless communication system, and more particularly, to a method and communication device for notification message transmission and reception of a natural disaster warning of the wireless communication system.
2. Description of the Prior Art
Earthquake and Tsunami Warning System (ETWS), set forth by the 3rd Generation Partnership Project (3GPP), introduces a means to deliver Warning Notification simultaneously to many mobile users who should evacuate from approaching Earthquake or Tsunami. The ETWS consists of a PLMN (Public Land Mobile Network) that is capable to deliver Warning Notification and user equipments (UEs) that are capable to receive Warning Notification. The PLMN of the ETWS can be a GERAN (GSM/EDEG radio access network) of a 2G/2.5G GSM system, a UTRAN (UMTS radio access network) of a 3G UMTS system, or a EUTRAN (evolved-UTAN) of a long term evolution (LTE) system. Warning Notification Providers, which are usually run by local governments, produce Warning Notification to PLMN operator when an earthquake or tsunami event occurs.
Warning Notification is classified into two types depending on the purpose and urgency of the notification. The first type of Notification is called Primary Notification that delivers the most important information of the threat that is approaching to users (e.g. the imminent occurrence of Earthquake or Tsunami) and shall be delivered to the users as soon as possible. For example, the Primary Notification can notify the UE of the disaster type. The second type of Notification is called Secondary Notification that delivers additional information, such as instructions on what to do or where to get help.
The Warning Notification Provider publishes a Primary Notification to PLMN and specifies the Notification Area where the Warning Notification is expected to be distributed when occurrence of a natural disaster is detected. Single or multiple Secondary Notifications are published following the Primary Notification. Finally, the Warning Notification Provider may request dissemination of notification to the PLMN to stop.
According to the related specifications so far, a primary notification message corresponding to the Primary Notification and a secondary notification message corresponding to the Secondary Notification are both provided by system information that is seen as broadcast information and transmitted on a BCCH (Broadcast Control Channel). The primary notification message is contained in a SIB10 (System Information Block Type 10), whereas the secondary notification message is contained in a SIB11 or multiple SIB11s.
The primary notification can occur at any point in time. A paging message is used for informing the UEs about presence of the primary notification. If the UE receives the paging message including “etws-PrimaryNotificationIndication”, the UE knows that the ETWS primary notification is present.
“etws-PrimaryNotificationIndication” is a value represented by one bit and included in the paging message to indicate “ETWS primary notification present”. When receiving this bit of the paging message, the UE immediately reads a SIB1 to find scheduling information for the SIB10 and read the SIB10 including the primary notification message.
The secondary notification message is allowed to be segmented, and the segments are transmitted via multiple SIB11s. Transmission cycles through the different segments belonging to a single secondary notification message at subsequent occasions for this SIB.
The PLMN possibly publishes several secondary notification messages with different content. Each of the secondary notification messages can be transmitted segment by segment via the SIB11. However, the abovementioned specifications do not specify any actions of the UE about how to know which secondary notification message each segment belongs to. When the UE does not identify which secondary notification message a received segment belongs to, the segments corresponding to different secondary notification messages may be combined together. In this situation, a decoding result of the complete secondary notification message turns out unreadable text content. Consequently, the user is not able to follow indication of the secondary notification message.
According to the abovementioned specifications, the UE receives the primary notification message after the paging message including the “etws-PrimaryNotificationIndication” is received. Then the UE receives the secondary notification message after a primary notification message is received. However, the secondary notification messages may be arrived at the UE before the primary notification message due to system information scheduling. In this situation, the UE is unable to receive the secondary notification message since the primary notification message has not been received. To achieve an emergent disaster notification system, the primary and secondary notification messages should be received as soon as possible.